How many calories a day have you been eating and what are these calories made up from, protein/carbs and fats wise and also what food stuffs.
Also what was your training routine. I had someone say the very same thing to me not so long back and he's gained 6lbs already in 3 weeks.
No supplement is going to magic pounds of muscle onto you, give us some more info and I am sure we can get you there mate
J